The invention is for use in the field of heating pipelines and vessels with metallic foil strip heaters using resistive heating elements. Expansion joints are necessary to eliminate mechanical stresses created by differences in the heat expansion rate of the metallic foil of the strip heaters and that of the pipeline or vessel being heated. With long strip heater systems, the heater strip expands sufficiently to damage electrical connector boxes and insulation where no means to accommodate expansion are provided. There is also a danger of uncontrolled buckling which can cause wire insulation failure and inadvertent electrical grounding. Reference is made to the co-pending applications entitled "Flat Conductor Heater", Ser. No. 938,591, filed Aug. 31, 1978 and "Flat Conductor to Round Conductor Connection System," Ser. No. 937,889, filed Aug. 31, 1978 and incorporated by reference herein.